The germinative cells of oral mucosa and epidermis differentiate into spinous, granular and keratinized cells sequentially. Keratohyalin granules (KHG) are a distinctive components of the granular layer. The aim of this proposal is to determine the role of keratohyalin in normal keratinization in mammalian oral mucosa and epidermis. Morphologic studies of previous investigators suggested that KHG may be a precursor of either the filamentous component component or the interfilamentous matrix of keratin. In the proposed studies newborn rat epidermis will be used as a model system. KHG has been isolated by two methods. The major fibrous and non-fibrous proteins will be isolated and purified from the stratum corneum. Antibodies to these s. corneum proteins will be produced. Relationships of KHG proteins to s. corneum proteins have been previously demonstrated by SDS-polyacrylamide gel electrophoresis. These relationships will be investigated further by biochemical and immunologic techniques. An hypothesis on the role of keratohyalin in keratinization will developed. The hypothesis will be tested in two situations in which KHG vary quantitatively and qualitatively: 1) in the development of fetal rat epidermis; and 2) in different portions of rat oral mucosa in which the type of KHG and the extent of keratinization vary. Immunoelectrophoresis, fluorescent and ferritin labeled antibodies will be used. The studies of oral mucosa will permit the comparison of proteins of different types of KHG, and the proteins of the keratinized layer of oral mucosa with those of the rat epidermis.